1. Field of the Invention
The invention relates to a cardiac valve with flaps pivoting on balls.
Use is at present made of valves installed on the cardiac muscle making it possible to replace defective natural valves. In general terms said valves comprise a ring for holding the valve on the muscle and which carries an articulation means for one or more members which are displaced under the action of the blood flow between an opening position corresponding to the desired outflow direction and a closed position corresponding to the reverse direction. The main qualities needed for such valves are a good sealing in the closed position, the creation of a limited pressure drop in the opening direction, slow wear and an inability to lead to coagulation and thromboses.
2. Discussion of the Related Art
Existing valves only make it possible to inadequately achieve these objectives. Among the existing systems, reference can firstly be made to valves in which the flap is displaced by alternative translation. The connection system to the ring is then a fitting constituted by an appropriately curved rod and the flap can be constituted by a ball or by a disk. These valves create a significant pressure drop in the opening direction, because the member continues to disturb the blood flow and they are also subject to friction and wear. For this reason valves have been developed, which have one or more flaps connected to the ring by pivots materializing off centred rotation axes, in such a way that the pressure of the blood is adequate for pivoting them. However, wear still exists, as do stress concentrations on the pivots and the adjacent parts of the flaps and ring. Moreover, it is far from easy to assemble such valves, because it is necessary to create elastic deformations in order to permit the insertion of the pivots into a cavity of the flap or the ring. Such an operation may lead to a deterioration of the coating of the coagulation-preventing materials, such as pyrocarbon, which normally cover the substrate material of the different parts.